Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$217.74	5.567%	$229.8616	$229.86	$229.85	$229.90
Purchase #2	$82.48	8.630%	$89.598	$89.60	$89.60	$89.60
Purchase #3	$89.62	9.798%	$98.401	$98.40	$98.40	$98.40
Purchase #4	$63.81	13.161%	$72.208	$72.21	$72.20	$72.20
Purchase #5	$40.82	12.422%	$45.8907	$45.89	$45.90	$45.90
Purchase #6	$218.97	9.650%	$240.1006	$240.10	$240.10	$240.10
Purchase #7	$73.93	7.641%	$79.579	$79.58	$79.60	$79.60
7 purchase totals =	$787.37		$855.6389	$855.64	$855.65	$855.70